Sizing polyamide filaments and yarns



United States Patent y 3 120,452 SIZING POLYAMTDEFILAMENTS AND YARNS Vincent J. Maser, Abington, and Frank J. Glavis, Elkins Park, Pa, assignors to Rohm dz Haas Company, Philadelphia, Pa., a corporation of Delaware No Drawing. Filed Oct. 19, 1961, Ser. No. 146,332v 2 Claims. (Cl. 117--138.8)

This invention relates to the treatment of polyamide filaments and yarns to reduce snagging of the filaments during such textile operations with them as weaving, knitting, looping, and seaming. The sizing treatment referred to is of the type that serves to unify or monofilize a multi-filament yarn or bundle to make it function during the textile operations essentially as a unitary member.

Many coating materials have been applied in the past for the sizing of nylon yarns. Most of those materials were found inadequate because of the lack of adhesion to the filaments and the tendency of the coating material to rub off on the surfaces of guides or other parts of the textile machines with which the yarns made contact during the operations mentioned. The rubbing off of the coating results in irregularities in the operation, irregularities in the fabrics obtained, and accumulation of dirt because of the deposit of the sizing material on the guides and other parts of the machines and the tendency of such deposits to collect dirt and transfer irregularities onto the yarn. Polyacrylic acid and mixtures of poly-vinyl alcohol and boric acid have generally become accepted sizing materials for polyamide filaments and yarns, and generally from 2 to 6% by weight of these materials is applied, the weight being based on the weight of the yarn.

In accordance with the present invention, it has been found that extremely elfective sizing of polyamide filaments and yarns can be obtained by the application of certain aliphatic polybasic acids. The acids found effective are oxalic, maleic, citric, tartaric, itaconic, diglycolic, and malic. These acids in some instances may be optically active and such acids may be applied either as one of the optical active isomers or as a racemic mixture.

The etfectiveness of these acids is surprising since closely related acids such as malonic, succinic and boric acids are completely ineffective for this purpose. There seems to be a high degree of specificity involved.

The acids applied in accordance with the present invention have been found so highly efiicient in their sizing action on polyamide yarns that it is generally necessary to apply only from /2 to 2% by Weight, based on the weight of the yarn, of the acid. Besides the fact that they are quite efiicient, they have other characteristic advantages.

They are readily removable, simply by neutralization in aqueous media, and upon removal the yarn is restored to its natural condition of bulk and loftiness. Many of these acids found etfective are non-toxic, being quite commonly used in foods. It is possible with most of these acids, especially the food acids, to maintain low conditions of corrosiveness in the normal conditions of application. The acids adhere well and cement together strongly on drying, but undergo no insolubilization as a result of resinification or chemical reaction with the yarn during drying at the customary temperatures employed in sizing and slashing equipment. While the acids are readily removable after they have served their purpose, by simple neutralization as stated, nevertheless it is unnecessary to take extreme care to assure absolutely complete removal since their aliphatic nature assures that no discoloration occurs on aging as a result of oxidation and so forth.

The sizing acids of the present invention may be applied to staple fiber yarns or to continuous filament yarns of polyamides of all types and to particularly to hexa- 3,120,452 Patented Feb. 4, 1964 methylene adipamide, commonly referred to as nylon, and caprolactam.

The acids may simply be applied from aqueous media made up at concentrations of 1 to 3% or more if desired. After application the excess may be removed by squeezing and then the yarns may be dried at suitable temperatures from room temperature to 45 C. The application may be made by means of rolls, immersion, wicks, spraying, slashers especially for warps, and/or by any other suitable equipment.

The aqueous acid solutions may include other textile treating agents as desired. For example, they may include wetting agents such as in an amount of 0.01 to 0.5 based on the bath, or lubricants in an amount of 0.01 to 0.5% in the bath. The lubricant may be either a water-soluble or emulsifiable type. It is also possible for one and the same material to serve more than one purpose such as modifying the yarn in respect to smoothness and softness and at the same time to act as a lubricant and/ or wetting agent. Corrosion inhibitors may be added if desired.

In the following examples which are illustrative of the present invention, the parts and percentages are by weight unless other-wise indicated.

Example 1 An aqueous solution of 5% citric acid was introduced into the size box of a two roll slasher. A warp of 70 denier/34 filaments bright nylon yarn having 15 turns per inch was passed through the size box at 35 yards per minute and dried on a seven-can drier. The temperatures of the cans were 160, 180, 190, 190, 190, 160 F., with the last can at room temperature. The filaments of the yarn thus treated were cemented together strongly, and when the warp was woven into a marquisette fabric (56 x 40) no appreciable fraying or snagging, yarn or filament breakage occurred. The acid was readily removed from the fabric by scouring.

Example 2 A narrow warp (1 inch, ends) of 40 denier, 13 filaments bright nylon yarn having one-half turn per inch was slashed with an aqueous solution of 5% tartaric acid. The slasher speed was seven yards per minute. The warp was dried on a three-can drier the temperatures of which were 250, 250, and (last) 80 F.

The warp was woven into a ribbon with 60 picks per inch of a 150 denier, 40 filament bright nylon yarn having two and one-half turns per inch.

The weaving was very efiicient. Negligible breakage of yarns or filaments occurred. The acid was readily removed from the fabric by normal scouring procedures.

Example 3 A 48-inch warp of 200 denier, 34 filaments bright nylon yarn having three-quarters of a turn per inch was slashed with an aqueous 5% solution of diglycolic acid. The sizing machines had three rubber squeeze rolls and five drying cans which operated, from first to last, at 185,

215, 220, 220, F. The speed was 6 yards per minute. There was no sticking of the sized yarns to the cans or build-up of diglycolic acid thereon.

The warp was woven into a plain weave fabric (62 x 52) without appreciable breaking of yarns and filaments.

Example 4 3 fraying during weaving and knitting and it showed substantially complete resistance to damage by abrasion when tested in a Walker Yarn Abrader.

Example 5 Example 4 was repeated using an aqueous solution of 3% dl-malic acid. The filaments of the sized yarn were cemented together very strongly and the yarn resisted snagging during weaving and knitting.

Example 6 An aqueous solution of 3% maleic acid was used instead of the oxalic acid in Example 4. The filaments of the yarn were bonded together strongly and the yarn resisted snagging during weaving and knitting.

Example 7 We claim:

1. A method of sizing a multi-filament polyamide yarn which comprises applying about /2 to 2% by weight, based on the Weight of the yarn, of a polybasic aliphatic acid selected from the group consisting of oxalic acid, malic acid, citric acid, tartaric acid, itaconic acid, diglycolic acid, and maleic acid, and then drying the yarn, the acid being applied by treatment of the yarn with an aqueous solution of the acid.

2. A textile yarn comprising a plurality of polyamide filaments sized by about /2 to 2% by weight, based on the weight of the yarn, of a polybasic aliphatic acid selected from the group consisting of oxalic acid, malic acid, citric acid, tartaric acid, itaconic acid, digylcolic acid, and maleic acid.

References (Iited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF SIZING A MULTI-FILAMENT POLYAMIDE YARN WHICH COMPRISES APPLYING ABOUT 1/2 TO 2% BY WEIGHT BASED ON THE WEIGHT OF THE YARN, OF A POLYBASIC ALIPHATIC ACID SELECTED FROM THE GROUP CONSISTING OF OXALIC ACID, MALIC ACID, CITRIC ACID, TARTARIC ACID, ITACONIC ACID, DIGLYCOLIC ACID, AND MALEIC ACID, AND THEN DRYING THE YARN, THE ACID BEING APPLIED BY TREATMENT OF THE YARN WITH AN AQUEOUS SOLUTION OF THE ACID. 